] So when Clark found the new generation of road sensor,
] Arnu drove out to help investigate further. The pair
] found that, at close range, they could use a handheld
] frequency counter to pick up the wireless signals given
] off by the devices as a car passes. Over the following
] month and half, Clark and Arnu engaged in a kind of
] geocaching game with the Men in Black, systematically
] sniffing out the road sensors with the frequency counter,
] exhuming them, and opening them up. They discovered that
] each device was coded with three-digit identifier that
] could be read off an internal dial, allowing Arnu to make
] a list that correlated each unit's I.D. number with its
] GPS coordinates, creating a virtual map of a portion of
] the surveillance network surrounding the Groom Lake
] facility. Some of the sensors were miles away from the
] base.

Interesting sensor network...